When Apple sued HTC, and targeted Android specifically (news which came out of the blue), many people, including myself, were convinced this was Apple letting the world know they were afraid of Android's rising popularity. This notion was laughed away by many an Apple fan, but it turns out that this is most likely far closer to reality than many dare to admit: in the first quarter of 2010, Android conquered the number two market share spot from the iPhone in the US - and by a wide margin too. Update: Added a graph which better shows the trend.

In this case, there are more than two major players, so it seems unlikely that one of them would establish majority and monopoly from there on. Also, a good portion of PCs success was due to Apple shooting its own foot (never used OS9, but have heard horror stories about it). Linux didn't have a decent UI then to compete for consumer market share.